Voice coil motors are commonly used in the disk drive industry to move a head positioner assembly relative to one or more rotating data storage disks. The head positioner assembly includes an actuator of any number of types/configurations (e.g., a single actuator arm, a plurality of stacked actuator arms, an actuator body with a plurality of actuator arm tips extending therefrom (e.g., an “E” block)). Other components of the head positioner assembly include a suspension for each data storage surface of each data storage disk incorporated in the drive, as well as a head mounted on each suspension. A head positioner assembly that includes a plurality of suspensions (and thereby a plurality of actuator arms or actuator arm tips) is commonly referred to in the art as a head stack assembly or HSA.
An upper voice coil motor (VCM) assembly and a lower voice coil motor (VCM) assembly of the voice coil motor are disposed in vertically spaced relation within the drive. One or both of the upper VCM assembly and the lower VCM assembly include a magnet and typically at least some type of a steel housing to provide a magnetic circuit path and to support/retain the magnet. A coil is appropriately mounted on the head positioner assembly, and is positioned in a space between the upper VCM assembly and the lower VCM assembly. The magnetic field causes the coil to move in a predetermined manner relative to the stationery upper VCM assembly and the stationery lower VCM assembly. This then causes the head positioner assembly to move so as to position each head at the desired track of its corresponding data storage disk.
The total amount of time required to move the head positioner assembly from one position to another position, and to thereafter be able to exchange information with the relevant data storage disk(s), obviously has an overall effect on disk drive operations. Vibration of the head positioner assembly may increase the amount of time for its various heads to settle on the correct track of the corresponding data storage disk. One could use a number approaches to address this condition. One would be to move the head positioner assembly at a slower rate. This may minimize/dampen vibrations, but is inefficient from a time standpoint. Another approach would be to move the head positioner assembly at a higher rate, and wait for the resulting vibrations to sufficiently dampen. This is also inefficient from a time standpoint.
Another approach to reducing the total amount of time required to move the head positioner assembly from one position to another, and to thereafter be able to exchange information with the relevant data storage disk(s), is to attempt to minimize mechanical vibrations of the head positioner assembly by somehow aligning the upper VCM assembly with the lower VCM assembly. All known techniques in the disk drive industry use a purely mechanical alignment or registration. Mechanical alignment not only increases costs since more precision is required for the manufacture of the upper VCM assembly, the lower VCM assembly, and/or tooling used to install the same, but purely mechanical alignments may not consistently magnetically align the upper VCM assembly with the lower VCM assembly. Out-of-plane magnetic field force components may then still exist, which may excite vibrational modes in the head positioner assembly, that in turn increases the seek or settle time of the drive's head(s).